If your family was the only one around, and giant beasts galloped or swooped down to prey on you, you might be as conservative as Grud Crood (voiced by Nicolas Cage). When the known world is a mortal threat, your cave is your fallout shelter. A Neanderthal in Cartoonland, Grud has honed his survival skills sufficiently to lead the Crood brood on a giant-egg hunt that plays like an NFL scrimmage. And like a football coach with a master sergeant’s mentality, he barks out orders— “Stay inside the family kill circle!” — to his wife and kids. His useful wariness, though, has festered into an almost religious apprehension. “Fear keeps us alive,” he warns in a sage voice. “Never not be afraid.”

The Croods, DreamWorks’ lively if nothing-new 3-D animated feature from directors Chris Sanders (Lilo & Stitch, How to Train Your Dragon) and Kirk De Micco, taps the familiar dynamic of cartoon families — the Flintstones, the Incredibles and the Simpsons — to tell a story of generational discord and eventual, inevitable reunion. Grud’s hot-bodied daughter Eep (Emma Stone), disobeying his stay-at-home rules to go climbing above their rock fortress, meets a cool guy named Guy (Ryan Reynolds), who just happens to have invented fire. The father is cautious, the teen girl adventurous, her new beau clever in a way that threatens Dad. Guess which one needs to be taught a lesson. For Grud, as with Homer Simpson, father knows least.

To extend the Simpsons analogy, Eep is an older, tomboyish Lisa; son Thunk (Clark Duke) is a doltish, unathletic Bart; mother Ugga (Catherine Keener) is a less fretful, less essential Marge; baby Sandy is a feral Maggie (and, like the youngest Simpson, communicates without words); and elderly Gran (Cloris Leachman) is crotchety, borderline-senile Abe with a sex change. That makes Guy one of those smart boys who has a one-episode fling with Lisa.

This orphan dream-boy is the Thomas Edison of pre-history. Besides fire, he’s also invented shoes, a rough form of instant photography and the domestication of wildlife: a monkey named Belt that holds up Guy’s pants. “Pets,” he explains to the Croods. “An animal you don’t eat.” A renegade from a slightly future world, Guy is as far ahead of the Croods as they are of Gran, who sports a reptilian tail. (At least Grud is all-mammal.) Evolution is in fast-forward here, and so are the earthquakes, volcano eruptions and other geological disasters facing the Croods. Where Grud believed survival meant staying put, Guy thinks homesteading spells disaster. Sensing a coming continental shift, Guy tells them, “Our world is ending, Tomorrow is a place where things are better.” He’s also the first climate-change alarmist.

Originally announced in 2005, when DreamWorks was to produce the movie with the stop-motion geniuses at Aardman Films and John Cleese was hired to write the script, The Croods creates two different landscapes: the stark, monochromatic Caveworld where the family lives, barely, and the wildly luscious, DayGlo Tomorrow area to which they must flee. The palette brought to life by Sanders, De Micco and their design team is rich indeed, in the perhaps overfamiliar Avatar style, and bursting with imaginative fauna from the same bestiary as Maurice Sendak’s Wild Things and Chuck Jones’s Roadrunner critters.

As Pixar movies have elaborated on the pictorial richness and serious undertone of old Disney classics, DreamWorks has updated the knockabout vaudeville shtick and brisk, impudent attitude that Jones and other Warner Bros. cartoon directors reveled in. When DreamWorks directors rev into full-farce mode, they can manufacture divine lunacy, as in last year’s Madagascar 3: Europe‘s Most Wanted.

The Croods shares Madagascar’s saucy visual sense and its exemplary voice cast; Stone’s delivery matches Eep’s verve, and Cage infuses his trademark vocal mopiness with stalwart undertones that indicate the caveman could become a hero. But the family-dramedy genre that the film inhabits demands a bit more narrative ingenuity than is on display. Until a late heart transplant, when Grud seizes the plot from the Eep-Guy romance to show that brute strength has its advantages, The Croods settles for forcing Grud and Guy into an intergenerational, opposites-attract road movie. It’s Identity Thief with flying piranhas, or Plains, Trains & Automobiles on foot.